Sergio Aguero is as valuable as Lionel Messi and Cristiano Ronaldo - Pellegrini

Manuel Pellegrini claims Sergio Aguero is worth as much to Manchester City as Lionel Messi and Cristiano Ronaldo are to their clubs.

And despite Aguero's stunning form for City this season, manager Pellegrini is convinced the Argentinian is going to get even better in the coming years.

Aguero continued his outstanding start to the season with a sensational hat-trick in City's dramatic 3-2 defeat of Bayern Munich in the Champions League in midweek.

The prolific Argentinian has now scored 17 goals this season and is again being compared with Barcelona star Messi and Real Madrid ace Ronaldo, the pair long acknowledged as the best in the game.

Pellegrini said: "Well of course I think that no-one can replace Messi at Barcelona, Ronaldo at Real Madrid or Sergio here - or a lot of very important players. It is not the same playing without Aguero as with Aguero.

"He has many years more to play here. I am always asking and demanding that he tries to be the best player because he has all the conditions to do that.

"That is why I am very glad for him he is always improving every day.

"I think he is a top player, a very important striker here in the Premier League and we are very glad to have him in our team."

Aguero, 26, is set to make his 100th Barclays Premier League appearance since joining City for £38million in 2011 as the champions travel to Southampton this weekend.

Only Alan Shearer (79) and Ruud van Nistelrooy (68) have scored more goals in their first 100 appearances than Aguero has in his first 99 (64).

Despite his prolific output, and virtually beating Bayern single-handedly in midweek, Pellegrini insists City are not a one-man team.

Aguero did score 28 goals in all competitions last season but his contribution in the second half of the campaign, as City closed out title success, was limited due to injuries.

Pellegrini said: "I always say we have a squad and if, for different reasons, Sergio cannot play, we must have another one that can do it.

James Olley's Top 10 Premier League strikers

James Olley's Top 10 Premier League strikers

1/10
10. Michael Owen

Forget the latter-day, injury ravaged incarnation and focus on the teen who took the world by storm around the turn of the Millennium. Brimming with pace, movement and a deadly eye for goal, he scored 118 League goals for Liverpool before adding 32 more at Newcastle and United.

2/10
9. Luis Suarez

A flawed genius who would have been higher on this list had he stayed at Liverpool. A Tazmanian Devil of a striker whipping up trouble wherever he went, allying industry and guile in an often unstoppable combination. Scored 69 goals in 110 League games.

Getty

3/10
8. Sergio Aguero

Aguero’s goal-to-game ratio is the best in League history and the only thing keeping him from climbing this list will be his longevity should he decide to leave Manchester City. 64 goals in 99 League games is a staggering return

4/10
7. Dennis Bergkamp

The Dutchman only scored 87 League goals but left an indelible mark. Oozed class and was vital to Arsenal’s Double-winning seasons of 1998 and 2002.

5/10
6. Andy Cole

Cole’s game was not particularly complicated but he was lethal inside the box, scoring 187 League goals — only Shearer has more. Won five titles at United and formed a deadly partnership with Dwight Yorke that led United to their Treble in 1999.

6/10
5. Wayne Rooney

On track to become United’s all-time leading scorer and has 177 League goals so far. Rooney has not always hit the heights he threatened to but he has provided some of the most memorable moments in League history and won the title five times.

7/10
4. Didier Drogba

A wrecking ball of a striker who epitomised the ruthlessness of Chelsea in Jose Mourinho’s first spell. He racked up three League titles, four FA Cups and exactly 100 League goals in his first spell at the club but was more than just a physical colossus.

8/10
3. Eric Cantona

He cost £1.2m from Leeds in 1992 yet his impact on Manchester United was priceless. Much has been made of United’s Class of ’92 but Cantona was their headmaster, leading from the front for two decades of domination.

9/10
2. Alan Shearer

The most prolific goalscorer the League has ever seen. Scored 260 goals for Southampton, Blackburn and Newcastle. One solitary title is the main reason he does not top this list but for consistency, he has few peers.

10/10
1. Thierry Henry

Allied class and clinical finishing over a long period better than anyone else. Henry scored 175 Premier League goals, won two titles and led from the front in Arsenal’s ‘Invincibles’ season. A brilliant talisman.

"We hope he continues the same way but I suppose Edin (Dzeko) will be fit next week and he can score also. This team we never depend just on one striker. The last (league) game, Sergio didn't score and we won with a goal from (Stevan) Jovetic and one from Yaya Toure. If you remember, we won the title here last year with a lot of games without Sergio.

"But, when he plays, it makes a difference."

Aguero was injured in January and in and out of the team for the rest of the season after that, and also hampered at the World Cup.

Because of that Pellegrini eased him back into action at the start of this campaign, and that decision looks to have paid off.

Pellegrini said: "You never know when a player will be injured but I think that this year we prepared him in the correct way.

"If you remember in the first three games, including the Community Shield, we didn't play with Sergio, we just gave him 20-25 minutes, no more, so he could have a good pre-season. He needed that after the last season when he had a lot of injuries.

"He is fit and we hope he will continue in this way until the end of the season."

Aguero has said that he views the game at Southampton as must-win, as it would enable City to leapfrog the high-flying Saints into second place.

City beat Swansea last weekend and are hoping to build some momentum with further games against Sunderland and Everton to come in the next week.

Pellegrini said: "Yes, it is an important game because we need the three points and we can be in the second place. It is always better to be second than third but it is not only this game.

"This is the first game of the three we must play this week in the Premier League and I hope after the three we can be second place and be near to Chelsea."